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Residential Roofing Basics and Roof Attachments

written by Johan Alfsen

Tilt

Navigating through cost hurdles

For years, solar installers have been challenged with the tricky task of mounting solar arrays to various roof types. Not only do they need to find the best engineered structural attachment to bear the load of the system, but they also have to ensure a watertight seal for all roof penetrations. Adding to these complicated decisions, is the endless amount of product options with various price tags and levels of quality. In an aggressively cost competitive market in the US, installation companies constantly look for ways to lower their cost per watt to win more customers going solar. While lowering the cost of solar is ultimately positive, this also tends to lead to more low-quality product options in the market. Manufacturers do their very best to avoid a “race to the bottom” scenario by balancing the cost vs quality ratio with innovation. K2 Systems has a history, dating back to the early 2000s, of creating high quality racking and mounting products in countries all around the world. The diversity of roof types across these countries naturally creates innovative solutions that has set the foreground for K2 USA and Mexico to develop cost competitive products for their specific markets.

Common roof types in the US

While there are many roof types in the US, the most common residential roofing systems faced by solar installers are composition asphalt shingle, tile, and metal. (For more information on low slope and commercial roofing systems see the Everest Q3 newsletter article)

Composition / Asphalt Shingle Roofs

Often referred to as comp, this roofing system is much easier to work on than tile roofs as they are flat and can be grippy. However, when granules loosen they can become slippery, especially on steeper pitched roofs. Working temperatures are crucial so as not to damage shingles when walking on them or working with roofing bars to installs flashings. Shingles also come with a bead of adhesive on the underside to self-adhere to other shingles and avoid water or debris intrusion. When breaking this seal be sure to reapply a compatible sealant to reinforce the bond. There are 3 main types of comp shingles in the US: Presidential, 3-Tab and High Definition.

presidential

1) Presidential

Presidential shingles are quickly becoming the norm as they are cost competitive, mid to high range quality, and have a lifespan that is anywhere from 20-30 years. They are straight forward and easy to work with with standard comp mounting systems.

rolled roof

2) 3-Tab

Popular over the years, 3-tab shingles tend to be the most cost effective, but have a lower lifespan of about 15 years, depending on the geographic location. They are much thinner than all the other shingle types and can easily be damaged by roofing bars so you need to be careful when working with these types of comp.

HD

3) High Definition

High definition shingles are typically installed on higher-end homes since they are the more expensive comp shingle roofing product. They have a lifespan range of 25-50 years, depending on the manufacturer. They are easy to identify by their staggered and thicker tabs. Most comp mount flashings are about 12 inches from top to bottom. In order to get flashing into the nail line and in the correct position for proper waterproofing, it’s common to fold and cut tabs that obstruct the flashing from being properly installed. The tabs are mostly decorative and should not compromise the waterproofing when a flashing is installed properly. (I will try and find a picture showing this).

SR

EverFlash eComp is the main composition roof attachment for K2 Systems US. There are two versions available that allow for both dual and shared rail. For standard dual rail systems EverFlash eComp is the primary product to use. For shared rail, you will want to use the EverFlash eComp Slider Kit to allow for adjustability. In order to position one rail for two rows of modules to meet with the CrossRail Shared Rail system, north/south adjustability is critical. The eComp Slider allows you to shift the L-Foot the full course of the shingle.

 

Comp shingle roof manufacturers will list out parameters and guidelines for proper installation of their products. Pitch will ultimately determine if shingles are appropriate for the roof slope as well as the type of underlayment, which can be specified to be felt paper, synthetic, or an adhered water barrier. Shingles are then layered and nailed to the sheathing in a pattern that secures all the shingles together to the roof. These nail patterns can sometimes obstruct a commonly sized 12 inch metal flashing so, at times nails will need to be removed to properly place the flashing into the nail line to be fully waterproofed. For detailed instructions on this, see our EverFlash Quick Guide.

Tile Roofs

Tile roofs are a very common roof type in big solar markets like CA, AZ, FL, and other parts of the southwest. Tile roofs can vary in shapes, sizes, and material. More modern tile roofs today are built with heavier-duty concrete tiles that interlock to each other, whereas older more traditional tiles consist of clay that can be fragile. Tile roofs have underlayment materials similar to comp, but have a gap between the tile and decking surface that is more susceptible to water and debris, making the underlayment the most critical part of the waterproofing of the roof. Some jurisdictions will require a “primary flashing” at the underlayment level as well as a top tile flashing. This can be commonly found with vent pipes, but as a retrofit this can be more challenging for solar installers as they are forced to use roofing tars, additional underlayment, or adhesives, thus taking more time for installation.

roofing

The common modern concrete tiles come in three main shapes of Flat tile, W-tile, and S-tile.

 

Each shape has different heights and thicknesses making mounting options somewhat more complicated. Having an international background, K2 has designed various tile hooks for many different tile roof types. K2 USA and Mexico has commonly used the Tile Hook 3S and the Flat Tile Hook to cover the most popular tile roofs.

Hooks

The Tile Hook 3S has adjustable heights to allow for various profile tiles and an aluminum arm that returns over the tile for better strength as the load is closer to the anchor point of the mount. It also uses a standard L-Foot that provides even more adjustability. The Flat Tile Hook is a simple steel hook that is robust and has a slanted upward shape to avoid deflection. The Flat Tile Hook design does not require an L-Foot and comes with the hardware included to mount the CrossRail directly to the hook.

roofing

Clay tiles are often referred to as cap and barrel tiles and are more traditional, but being installed less and less. These tiles are sometimes adhered together with a foam or concrete. This is common in Florida where wind speeds are higher. In CA and the Southwest the tiles can be hooked in with wires. Naturally these clay tiles are much more fragile than concrete tiles, making it hard to walk on and work with. Due to the fragile nature of the tiles, many times the installer and/or roofers will strip away the clay tiles and install comp shingles in the area of the array and then surround it with tile to make it appear as tile. This is referred to as an inlay or picture frame system. If done correctly, this style can be longer lasting, better water resistant, and look more like a building integrated system (BIPV).

Metal Roofs

Metals roofs can be found all over the world. In the US they are more commonly found where there is snow and rain like the mid and north west. There are various styles and profiles of metal roofs, but the most popular are standing seam, trapezoidal, and corrugated. While trapezoidal and corrugated roofs have basic shapes, standing seam roofs can have many different profiles and interlocking styles.

PowerClamps

K2 US and Mexico have the non-penetrating standing seam clamp called the PowerClamp. The PowerClamp is available in both a Standard (double pin) and Mini (single pin) option. This simple design covers the more common standing seam profiles in the market.

 

Other manufacturers such as Solar Connections and S5 carry a variety of clamps, both penetrating and non-penetrating for all the different metal roof types.

roofing

For trapezoidal roofs, K2 has developed the MiniRail XPRess System. A clever design that attached a short rail section that simply attaches to the top portion of the trapezoidal roof with self tapping metal screws. The bottom of the base also comes with a pre-installed EPDM pad to self seal the penetrations. This helps to avoid having to search and find rafters for connections. The 17” mini rail allows the installer to bridge the gap between the trapezoidal peaks and connect between modules running east to west. This reduces materials and provides a low profile aesthetic.

There are many other roof types not discussed here, such as slate, wood shake, metal shingles, synthetics, etc. These are less common, but do exist. A good way to determine a proper mounting and flashing solution for less common roofs like these is to observe and, if possible, mimic other roof protrusions such as vent pipes. The best way to understand any roof type, common or not, is to first understand how the roofing system is built. Doing as much research on the roof type before installation is essential to understanding the system and choosing the best mounting and flashing products. Installers should investigate who the roof manufacturer is, if there are warranties in place, and read through manuals, guidelines and best practices to ensure a quality installation.

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